The disclosure is directed to an apparatus and method of use of the apparatus for producing from a natural gas well. More particularly, this relates to a partially depleted reservoir production procedure. As the internal pressure drive of a partially depleted formation is reduced over a period of time, it is generally expedient to shift to intermittent production of liquid slugs to efficiently produce the formation. This typically involves the installation of intermittent gas lift system, and one version of such equipment is the installation of a plunger which separates an accumulated liquid slug to be driven up the well by the gas propellant. By this approach, formation gas is obtained and various liquid from the formation are likewise produced. Such liquids typically include condensates which might otherwise collect as droplets on the tubing wall.
An exemplary system is identified in U.S. Pat. No. 4,211,279. This shows a wellhead apparatus connected with a tubing string installed in a casing. It further includes a plunger catcher which holds the free-fall plunger at its uppermost position to permit gas to escape from the tubing string. Moreoever, it cooperates with a timer to adjust the cycle duration to thereby obtain the desired production rate.
Similar disclosures are found at U.S. Pat. Nos. 4,575,044, 3,545,540, 3,424,066 and 2,918,015. In very general terms, the various references set forth systems of apparatus including wellhead devices, plungers of all types and descriptions, and valves which connect with downstream gas consuming facilities. For instance, the downstream line may connect through a valve to a gas gathering system.
Service of the wellhead apparatus is an important factor. The context includes certain service requirements. In general, this type equipment is installed on wells which are in the twilight zone of their productive lives. At this stage, the well may have been serviced for a number of years. Typically, it has a formation gas drive which is adequate for some purposes, but which is typically inadequate to lift liquid condensates. This causes liquids to accumulate at or near the bottom. When liquids accumulate, they create problems in continued production. One of the problems relates to the collection of condensate along the tubing wall. While the condensate typically always includes some petroleum products, they may also include salt water, thereby running the risk of forming rust in the tubing string or the wellhead apparatus. Thereafter, the installation of a reciprocating free-fall plunger in the system tends to scrape the rust fro the pipe wall, thereby increasing the risk of damage to the tubing string and the wellhead apparatus. Moreover, the reciprocating plunger has substantial impact at the termination of the free-fall cycle. This tends to wear the plunger and may damage the plunger, thereby forming an impact so great that wear and tear requires periodic maintenance. It is difficult to maintain old equipment. Especially this is so if the well is 20 or 30 years old. Often, it will be necessary to pull the tubing string, install new packers, repair holes in the casing and the like. Even when a less intrusive repair sequence is required, as for instance by merely removing the wellhead equipment, the repairs are tedious and difficult on the old equipment. The present invention is a wellhead apparatus which makes it much easier to repair the equipment. The present invention is an overhead wellhead apparatus which has an upwardly extending lubricator extension pipe located above a tee where the tee directs produced gas laterally. The overhead equipment is particularly advantageous in that the very top end of the lubricator extension terminates at a closed housing which supports an internally located piston. The plunger is permitted to travel upwardly through the lubricator extension. A plunger intercept mechanism is located therein, and is compressed momentarily by the traveling plunger. The intercept mechanism is compressively loaded. This cushions the shock of stopping the plunger. Moreover, all of this equipment is located above a connective flange which enables the lubricator extension to be selectively removed. The well is sealed off by means of a union above the master valve for easy disconnection.
One important feature of the present apparatus is the use of a flanged shoulder at the lubricator extension which is located above the tee. This coacting arrangement routinely enables the lubricator extension to be disconnected. Keep in mind that the lubricator extension may extend several feet above the ground at the wellhead. Service on this equipment is required long after the original drilling rig and workover rigs have been moved away from the location. This equipment stands substantially up in the air and is difficult to service. The present apparatus incorporates an upstanding, adjacently located vertical ladder having a frame member for supporting a laterally extending arm at the top, the arm being positioned over the lubricator extension. It has a protruding arm which terminates at a swivel, thereby permitting the lubricator extension to be disconnected and swung to the side. The lubricator extension is joined serially in line by means of a union nut clamping opposing flanges for connection of the lubricator extension and a lubricator extension union sub therebelow. The union sub is serially connected above the tee.
This apparatus thus permits easy service. Service is implemented at a time when the plunger is caught in the lubricator extension or is located downhole. In either case, the lubricator extension breaks free and swings to the side. This particularly is important to enabling others to have access to thereby furnish maintenance and service on the equipment. Through a use of a quickly disconnected union, service personnel can remove the union nut, make a disconnection at the bottom of the lubricator extension at a mating flange on the lubricator extension union sub, swing the components apart, and completely service the equipment in this fashion. Moreover, this can be done with the plunger at any location including in the lubricator extension.
The present disclosure is likewise directed to a method of operating the plunger in relation to the amount of fluid produced, shut-in interval and plunger travel time. Generally, it is desirable to operate the system so that the plunger brings to the surface an optimum measure of produced liquid. If excessive accumulation downhole occurs, it is difficult to produce gas through the standing column of liquid. On the other hand, if excessive numbers of trips of the plunger occur, then the gas fluid drive is usually insufficient and the equipment tends to wear out more rapidly. The formation is probably depleted more rapidly, perhaps to the detriment of the formation. It should be recalled that excessive production rates are damaging to the formation and may lead to small capillary blinding or failure of the flow channels in the same formation extending to the well borehole. In any event, it is desirable to produce the well at a controlled rate and the present method contemplates such a controlled rate of production which correlates these variables. More will be noted on this method of operation hereinafter.